Fast Facts About Cookiecutter Sharks

The cookiecutter shark is a small shark species who got its name from the round, deep wounds it leaves on its prey. They are also known as the cigar shark, luminous shark, and cookie-cutter or cookie cutter shark.

The cookiecutter shark's scientific name is Isistius brasiliensis. The genus name is a reference to Isis, the Egyptian goddess of light, and their species name is a reference to their distribution, which includes Brazilian waters. 

Classification

• Kingdom: Animalia
• Phylum: Chordata
• Subphylum: Vertebrata
• Superclass: Gnathostomata
• Superclass: Pisces
• Class: Elasmobranchii
• Subclass: Neoselachii
• Infraclass: Selachii
• Superorder: Squalomorphi
• Order: Squaliformes
• Family: Dalatiidae
• Genus: Isistius
• Species: brasiliensis

Description

Cookiecutter sharks are relatively small. They grow to about 22 inches in lengths, with females growing longer than males. Cookiecutter sharks have a short snout, dark brown or grayish back, and light underside. Around their gills, they have a dark brown band, which, along with their shape, gave them the nickname cigar shark. Other identification features include the presence of two paddle-shaped pectoral fins, which have a lighter coloration on their edges, two small dorsal fins near the back of their body and two pelvic fins.

One interesting characteristic of these sharks is that they can produce a greenish glow using photophores, bioluminescent organs which are located on the shark's body, but densest on their underside. The glow can attract prey, and also camouflages the shark by eliminating its shadow.

One of the most important features of cookiecutter sharks is their teeth. Although the sharks are small, their teeth are fearsome-looking. They have small teeth in their upper jaw and 25 to 31 triangular-shaped in their lower jaw. Unlike most sharks, who lose their teeth one at a time, cookiecutter sharks lose the complete section of lower teeth at once, as the teeth are all connected at their base. The shark ingests the teeth as they are lost -- a behavior that is thought to be related to increasing calcium intake. The teeth are used in combination with their lips, which can attach to prey through suction. 

Habitat and Distribution

Cookiecutter sharks are found in tropical waters in the Atlantic, Pacific, and Indian Oceans. They are often found near oceanic islands. 

These sharks undertake a daily vertical migration, spending the daytime in deep waters below 3,281 feet and moving toward the water surface at night. 

Feeding Habits

Cookiecutter sharks often prey upon animals much larger than they are. Their prey includes marine mammals such as seals, whales and dolphins and large fish such as tuna, sharks, stingrays, marlin and dolphin, and invertebrates such as squid and crustaceans. The greenish light given off by the photophore attract prey. As the prey approaches, the cookiecutter shark quickly latches on and then spins, which removes the prey's flesh and leaves a distinctive crater-like, smooth-edged wound. The shark grips the prey's flesh using its upper teeth. These sharks are also thought to cause damage to submarines by biting their nose cones.

Reproductive Habits

Much of cookiecutter shark reproduction is still a mystery. Cookiecutter sharks are ovoviviparous. The pups inside the mother are nourished by the yolk inside their egg case. Cookiecutter sharks have 6 to 12 young per litter.

Shark Attacks and Conservation

Although the idea of an encounter with a cookie cutter shark is frightening, they generally present no danger to humans due to their preference for deep waters and their small size. 

The cookiecutter shark is listed as a species of least concern on the IUCN Red List. While they are caught occasionally by fisheries, there is no targeted harvesting of this species. 

Sources

• Bailly, N. 2014. Isistius brasiliensis (Quoy & Gaimard, 1824). In: Froese, R. and D. Pauly. Editors. (2014) FishBase. Accessed through: World Register of Marine Species, December 15, 2014
• Bester, C. Cookiecutter Shark. Florida Museum of Natural History. Accessed December 15, 2014.
• Compangno, L., ed. 2005. Sharks of the World. Princeton University Press. 368pp.
• Martin, R. A. Cookiecutter Shark. ReefQuest Centre for Shark Research. Accessed December 15, 2014.